Preview render view is noisy, not sure what I did or how to fix it
As m.ardito says, "previews are just... previews"

Unless you set your preview sample value to something very high, you wont get good results like the final render. In fact, that is why it is called a preview. The point of a preview is to render the file fast so you can look at how it will change in the final render. In preview mode it is easier to make materials and change lights.

If you want a higher quality preview image, just increase the samples under "preview." But, be warned, setting the sample size to something higher takes much longer to preview.